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Source code for tornado.ioloop

#!/usr/bin/env python## Copyright 2009 Facebook## Licensed under the Apache License, Version 2.0 (the "License"); you may# not use this file except in compliance with the License. You may obtain# a copy of the License at## http://www.apache.org/licenses/LICENSE-2.0## Unless required by applicable law or agreed to in writing, software# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the# License for the specific language governing permissions and limitations# under the License."""An I/O event loop for non-blocking sockets.Typical applications will use a single `IOLoop` object, in the`IOLoop.instance` singleton. The `IOLoop.start` method should usuallybe called at the end of the ``main()`` function. Atypical applications mayuse more than one `IOLoop`, such as one `IOLoop` per thread, or per `unittest`case.In addition to I/O events, the `IOLoop` can also schedule time-based events.`IOLoop.add_timeout` is a non-blocking alternative to `time.sleep`."""from__future__importabsolute_import,division,with_statementimportdatetimeimporterrnoimportheapqimportosimportloggingimportselectimportthreadimportthreadingimporttimeimporttracebackfromtornadoimportstack_contexttry:importsignalexceptImportError:signal=Nonefromtornado.platform.autoimportset_close_exec,Waker

[docs]classIOLoop(object):"""A level-triggered I/O loop. We use epoll (Linux) or kqueue (BSD and Mac OS X; requires python 2.6+) if they are available, or else we fall back on select(). If you are implementing a system that needs to handle thousands of simultaneous connections, you should use a system that supports either epoll or queue. Example usage for a simple TCP server:: import errno import functools import ioloop import socket def connection_ready(sock, fd, events): while True: try: connection, address = sock.accept() except socket.error, e: if e.args[0] not in (errno.EWOULDBLOCK, errno.EAGAIN): raise return connection.setblocking(0) handle_connection(connection, address) sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0) sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) sock.setblocking(0) sock.bind(("", port)) sock.listen(128) io_loop = ioloop.IOLoop.instance() callback = functools.partial(connection_ready, sock) io_loop.add_handler(sock.fileno(), callback, io_loop.READ) io_loop.start() """# Constants from the epoll module_EPOLLIN=0x001_EPOLLPRI=0x002_EPOLLOUT=0x004_EPOLLERR=0x008_EPOLLHUP=0x010_EPOLLRDHUP=0x2000_EPOLLONESHOT=(1<<30)_EPOLLET=(1<<31)# Our events map exactly to the epoll eventsNONE=0READ=_EPOLLINWRITE=_EPOLLOUTERROR=_EPOLLERR|_EPOLLHUP# Global lock for creating global IOLoop instance_instance_lock=threading.Lock()def__init__(self,impl=None):self._impl=implor_poll()ifhasattr(self._impl,'fileno'):set_close_exec(self._impl.fileno())self._handlers={}self._events={}self._callbacks=[]self._callback_lock=threading.Lock()self._timeouts=[]self._running=Falseself._stopped=Falseself._thread_ident=Noneself._blocking_signal_threshold=None# Create a pipe that we send bogus data to when we want to wake# the I/O loop when it is idleself._waker=Waker()self.add_handler(self._waker.fileno(),lambdafd,events:self._waker.consume(),self.READ)@staticmethod

[docs]definstance():"""Returns a global IOLoop instance. Most single-threaded applications have a single, global IOLoop. Use this method instead of passing around IOLoop instances throughout your code. A common pattern for classes that depend on IOLoops is to use a default argument to enable programs with multiple IOLoops but not require the argument for simpler applications:: class MyClass(object): def __init__(self, io_loop=None): self.io_loop = io_loop or IOLoop.instance() """ifnothasattr(IOLoop,"_instance"):withIOLoop._instance_lock:ifnothasattr(IOLoop,"_instance"):# New instance after double checkIOLoop._instance=IOLoop()returnIOLoop._instance

@staticmethod

[docs]definitialized():"""Returns true if the singleton instance has been created."""returnhasattr(IOLoop,"_instance")

[docs]definstall(self):"""Installs this IOloop object as the singleton instance. This is normally not necessary as `instance()` will create an IOLoop on demand, but you may want to call `install` to use a custom subclass of IOLoop. """assertnotIOLoop.initialized()IOLoop._instance=self

[docs]defclose(self,all_fds=False):"""Closes the IOLoop, freeing any resources used. If ``all_fds`` is true, all file descriptors registered on the IOLoop will be closed (not just the ones created by the IOLoop itself). Many applications will only use a single IOLoop that runs for the entire lifetime of the process. In that case closing the IOLoop is not necessary since everything will be cleaned up when the process exits. `IOLoop.close` is provided mainly for scenarios such as unit tests, which create and destroy a large number of IOLoops. An IOLoop must be completely stopped before it can be closed. This means that `IOLoop.stop()` must be called *and* `IOLoop.start()` must be allowed to return before attempting to call `IOLoop.close()`. Therefore the call to `close` will usually appear just after the call to `start` rather than near the call to `stop`. """self.remove_handler(self._waker.fileno())ifall_fds:forfdinself._handlers.keys()[:]:try:os.close(fd)exceptException:logging.debug("error closing fd %s",fd,exc_info=True)self._waker.close()self._impl.close()

[docs]defadd_handler(self,fd,handler,events):"""Registers the given handler to receive the given events for fd."""self._handlers[fd]=stack_context.wrap(handler)self._impl.register(fd,events|self.ERROR)

[docs]defupdate_handler(self,fd,events):"""Changes the events we listen for fd."""self._impl.modify(fd,events|self.ERROR)

[docs]defremove_handler(self,fd):"""Stop listening for events on fd."""self._handlers.pop(fd,None)self._events.pop(fd,None)try:self._impl.unregister(fd)except(OSError,IOError):logging.debug("Error deleting fd from IOLoop",exc_info=True)

[docs]defset_blocking_signal_threshold(self,seconds,action):"""Sends a signal if the ioloop is blocked for more than s seconds. Pass seconds=None to disable. Requires python 2.6 on a unixy platform. The action parameter is a python signal handler. Read the documentation for the python 'signal' module for more information. If action is None, the process will be killed if it is blocked for too long. """ifnothasattr(signal,"setitimer"):logging.error("set_blocking_signal_threshold requires a signal module ""with the setitimer method")returnself._blocking_signal_threshold=secondsifsecondsisnotNone:signal.signal(signal.SIGALRM,actionifactionisnotNoneelsesignal.SIG_DFL)

[docs]defset_blocking_log_threshold(self,seconds):"""Logs a stack trace if the ioloop is blocked for more than s seconds. Equivalent to set_blocking_signal_threshold(seconds, self.log_stack) """self.set_blocking_signal_threshold(seconds,self.log_stack)

[docs]deflog_stack(self,signal,frame):"""Signal handler to log the stack trace of the current thread. For use with set_blocking_signal_threshold. """logging.warning('IOLoop blocked for %f seconds in\n%s',self._blocking_signal_threshold,''.join(traceback.format_stack(frame)))

[docs]defstart(self):"""Starts the I/O loop. The loop will run until one of the I/O handlers calls stop(), which will make the loop stop after the current event iteration completes. """ifself._stopped:self._stopped=Falsereturnself._thread_ident=thread.get_ident()self._running=TruewhileTrue:poll_timeout=3600.0# Prevent IO event starvation by delaying new callbacks# to the next iteration of the event loop.withself._callback_lock:callbacks=self._callbacksself._callbacks=[]forcallbackincallbacks:self._run_callback(callback)ifself._timeouts:now=time.time()whileself._timeouts:ifself._timeouts[0].callbackisNone:# the timeout was cancelledheapq.heappop(self._timeouts)elifself._timeouts[0].deadline<=now:timeout=heapq.heappop(self._timeouts)self._run_callback(timeout.callback)else:seconds=self._timeouts[0].deadline-nowpoll_timeout=min(seconds,poll_timeout)breakifself._callbacks:# If any callbacks or timeouts called add_callback,# we don't want to wait in poll() before we run them.poll_timeout=0.0ifnotself._running:breakifself._blocking_signal_thresholdisnotNone:# clear alarm so it doesn't fire while poll is waiting for# events.signal.setitimer(signal.ITIMER_REAL,0,0)try:event_pairs=self._impl.poll(poll_timeout)exceptException,e:# Depending on python version and IOLoop implementation,# different exception types may be thrown and there are# two ways EINTR might be signaled:# * e.errno == errno.EINTR# * e.args is like (errno.EINTR, 'Interrupted system call')if(getattr(e,'errno',None)==errno.EINTRor(isinstance(getattr(e,'args',None),tuple)andlen(e.args)==2ande.args[0]==errno.EINTR)):continueelse:raiseifself._blocking_signal_thresholdisnotNone:signal.setitimer(signal.ITIMER_REAL,self._blocking_signal_threshold,0)# Pop one fd at a time from the set of pending fds and run# its handler. Since that handler may perform actions on# other file descriptors, there may be reentrant calls to# this IOLoop that update self._eventsself._events.update(event_pairs)whileself._events:fd,events=self._events.popitem()try:self._handlers[fd](fd,events)except(OSError,IOError),e:ife.args[0]==errno.EPIPE:# Happens when the client closes the connectionpasselse:logging.error("Exception in I/O handler for fd %s",fd,exc_info=True)exceptException:logging.error("Exception in I/O handler for fd %s",fd,exc_info=True)# reset the stopped flag so another start/stop pair can be issuedself._stopped=Falseifself._blocking_signal_thresholdisnotNone:signal.setitimer(signal.ITIMER_REAL,0,0)

[docs]defstop(self):"""Stop the loop after the current event loop iteration is complete. If the event loop is not currently running, the next call to start() will return immediately. To use asynchronous methods from otherwise-synchronous code (such as unit tests), you can start and stop the event loop like this:: ioloop = IOLoop() async_method(ioloop=ioloop, callback=ioloop.stop) ioloop.start() ioloop.start() will return after async_method has run its callback, whether that callback was invoked before or after ioloop.start. Note that even after `stop` has been called, the IOLoop is not completely stopped until `IOLoop.start` has also returned. """self._running=Falseself._stopped=Trueself._waker.wake()

[docs]defrunning(self):"""Returns true if this IOLoop is currently running."""returnself._running

[docs]defadd_timeout(self,deadline,callback):"""Calls the given callback at the time deadline from the I/O loop. Returns a handle that may be passed to remove_timeout to cancel. ``deadline`` may be a number denoting a unix timestamp (as returned by ``time.time()`` or a ``datetime.timedelta`` object for a deadline relative to the current time. Note that it is not safe to call `add_timeout` from other threads. Instead, you must use `add_callback` to transfer control to the IOLoop's thread, and then call `add_timeout` from there. """timeout=_Timeout(deadline,stack_context.wrap(callback))heapq.heappush(self._timeouts,timeout)returntimeout

[docs]defremove_timeout(self,timeout):"""Cancels a pending timeout. The argument is a handle as returned by add_timeout. """# Removing from a heap is complicated, so just leave the defunct# timeout object in the queue (see discussion in# http://docs.python.org/library/heapq.html).# If this turns out to be a problem, we could add a garbage# collection pass whenever there are too many dead timeouts.timeout.callback=None

[docs]defadd_callback(self,callback):"""Calls the given callback on the next I/O loop iteration. It is safe to call this method from any thread at any time. Note that this is the *only* method in IOLoop that makes this guarantee; all other interaction with the IOLoop must be done from that IOLoop's thread. add_callback() may be used to transfer control from other threads to the IOLoop's thread. """withself._callback_lock:list_empty=notself._callbacksself._callbacks.append(stack_context.wrap(callback))iflist_emptyandthread.get_ident()!=self._thread_ident:# If we're in the IOLoop's thread, we know it's not currently# polling. If we're not, and we added the first callback to an# empty list, we may need to wake it up (it may wake up on its# own, but an occasional extra wake is harmless). Waking# up a polling IOLoop is relatively expensive, so we try to# avoid it when we can.self._waker.wake()

[docs]defhandle_callback_exception(self,callback):"""This method is called whenever a callback run by the IOLoop throws an exception. By default simply logs the exception as an error. Subclasses may override this method to customize reporting of exceptions. The exception itself is not passed explicitly, but is available in sys.exc_info. """logging.error("Exception in callback %r",callback,exc_info=True)

class_Timeout(object):"""An IOLoop timeout, a UNIX timestamp and a callback"""# Reduce memory overhead when there are lots of pending callbacks__slots__=['deadline','callback']def__init__(self,deadline,callback):ifisinstance(deadline,(int,long,float)):self.deadline=deadlineelifisinstance(deadline,datetime.timedelta):self.deadline=time.time()+_Timeout.timedelta_to_seconds(deadline)else:raiseTypeError("Unsupported deadline %r"%deadline)self.callback=callback@staticmethoddeftimedelta_to_seconds(td):"""Equivalent to td.total_seconds() (introduced in python 2.7)."""return(td.microseconds+(td.seconds+td.days*24*3600)*10**6)/float(10**6)# Comparison methods to sort by deadline, with object id as a tiebreaker# to guarantee a consistent ordering. The heapq module uses __le__# in python2.5, and __lt__ in 2.6+ (sort() and most other comparisons# use __lt__).def__lt__(self,other):return((self.deadline,id(self))<(other.deadline,id(other)))def__le__(self,other):return((self.deadline,id(self))<=(other.deadline,id(other)))

[docs]classPeriodicCallback(object):"""Schedules the given callback to be called periodically. The callback is called every callback_time milliseconds. `start` must be called after the PeriodicCallback is created. """def__init__(self,callback,callback_time,io_loop=None):self.callback=callbackself.callback_time=callback_timeself.io_loop=io_looporIOLoop.instance()self._running=Falseself._timeout=None

[docs]defstart(self):"""Starts the timer."""self._running=Trueself._next_timeout=time.time()self._schedule_next()

[docs]defstop(self):"""Stops the timer."""self._running=Falseifself._timeoutisnotNone:self.io_loop.remove_timeout(self._timeout)self._timeout=None

class_EPoll(object):"""An epoll-based event loop using our C module for Python 2.5 systems"""_EPOLL_CTL_ADD=1_EPOLL_CTL_DEL=2_EPOLL_CTL_MOD=3def__init__(self):self._epoll_fd=epoll.epoll_create()deffileno(self):returnself._epoll_fddefclose(self):os.close(self._epoll_fd)defregister(self,fd,events):epoll.epoll_ctl(self._epoll_fd,self._EPOLL_CTL_ADD,fd,events)defmodify(self,fd,events):epoll.epoll_ctl(self._epoll_fd,self._EPOLL_CTL_MOD,fd,events)defunregister(self,fd):epoll.epoll_ctl(self._epoll_fd,self._EPOLL_CTL_DEL,fd,0)defpoll(self,timeout):returnepoll.epoll_wait(self._epoll_fd,int(timeout*1000))class_KQueue(object):"""A kqueue-based event loop for BSD/Mac systems."""def__init__(self):self._kqueue=select.kqueue()self._active={}deffileno(self):returnself._kqueue.fileno()defclose(self):self._kqueue.close()defregister(self,fd,events):iffdinself._active:raiseIOError("fd %d already registered"%fd)self._control(fd,events,select.KQ_EV_ADD)self._active[fd]=eventsdefmodify(self,fd,events):self.unregister(fd)self.register(fd,events)defunregister(self,fd):events=self._active.pop(fd)self._control(fd,events,select.KQ_EV_DELETE)def_control(self,fd,events,flags):kevents=[]ifevents&IOLoop.WRITE:kevents.append(select.kevent(fd,filter=select.KQ_FILTER_WRITE,flags=flags))ifevents&IOLoop.READornotkevents:# Always read when there is not a writekevents.append(select.kevent(fd,filter=select.KQ_FILTER_READ,flags=flags))# Even though control() takes a list, it seems to return EINVAL# on Mac OS X (10.6) when there is more than one event in the list.forkeventinkevents:self._kqueue.control([kevent],0)defpoll(self,timeout):kevents=self._kqueue.control(None,1000,timeout)events={}forkeventinkevents:fd=kevent.identifkevent.filter==select.KQ_FILTER_READ:events[fd]=events.get(fd,0)|IOLoop.READifkevent.filter==select.KQ_FILTER_WRITE:ifkevent.flags&select.KQ_EV_EOF:# If an asynchronous connection is refused, kqueue# returns a write event with the EOF flag set.# Turn this into an error for consistency with the# other IOLoop implementations.# Note that for read events, EOF may be returned before# all data has been consumed from the socket buffer,# so we only check for EOF on write events.events[fd]=IOLoop.ERRORelse:events[fd]=events.get(fd,0)|IOLoop.WRITEifkevent.flags&select.KQ_EV_ERROR:events[fd]=events.get(fd,0)|IOLoop.ERRORreturnevents.items()class_Select(object):"""A simple, select()-based IOLoop implementation for non-Linux systems"""def__init__(self):self.read_fds=set()self.write_fds=set()self.error_fds=set()self.fd_sets=(self.read_fds,self.write_fds,self.error_fds)defclose(self):passdefregister(self,fd,events):iffdinself.read_fdsorfdinself.write_fdsorfdinself.error_fds:raiseIOError("fd %d already registered"%fd)ifevents&IOLoop.READ:self.read_fds.add(fd)ifevents&IOLoop.WRITE:self.write_fds.add(fd)ifevents&IOLoop.ERROR:self.error_fds.add(fd)# Closed connections are reported as errors by epoll and kqueue,# but as zero-byte reads by select, so when errors are requested# we need to listen for both read and error.self.read_fds.add(fd)defmodify(self,fd,events):self.unregister(fd)self.register(fd,events)defunregister(self,fd):self.read_fds.discard(fd)self.write_fds.discard(fd)self.error_fds.discard(fd)defpoll(self,timeout):readable,writeable,errors=select.select(self.read_fds,self.write_fds,self.error_fds,timeout)events={}forfdinreadable:events[fd]=events.get(fd,0)|IOLoop.READforfdinwriteable:events[fd]=events.get(fd,0)|IOLoop.WRITEforfdinerrors:events[fd]=events.get(fd,0)|IOLoop.ERRORreturnevents.items()# Choose a poll implementation. Use epoll if it is available, fall back to# select() for non-Linux platformsifhasattr(select,"epoll"):# Python 2.6+ on Linux_poll=select.epollelifhasattr(select,"kqueue"):# Python 2.6+ on BSD or Mac_poll=_KQueueelse:try:# Linux systems with our C module installedfromtornadoimportepoll_poll=_EPollexceptException:# All other systemsimportsysif"linux"insys.platform:logging.warning("epoll module not found; using select()")_poll=_Select